Event variable improvements; Scripting/SDK improvements; New examples; Bug fixes.
Developing enough features for a full 3D engine in Construct is likely many years worth of work. There is an endless list of complex features that true 3D engines usually support: 3D collisions, 3D physics, animated 3D models, screen-space ambient occlusion, lighting, shadows, deferred rendering, physically modelled materials, various 3D-specific optimizations, and on and on and on. So yes, adding more features for 3D is very difficult and an endless amount of complicated and time-consuming work. Construct remains primarily a 2D engine with some basic 3D features which you can often use to good creative effect (take a look at examples tagged 3D in the Example Browser). If you want more advanced 3D, and you can make things work by embedding three.js, then you get a fully-featured 3D engine with all that already available right now. Otherwise if you want more advanced 3D built-in to Construct, you may be waiting for many years to come.
I have managed lighting, shadows, 3d collisions and 3d physics to a certain degree purely in vanilla events. Aslong as the current batch of 3d plugins remain supported can still do some interesting things without touching code. :)
It is pretty OK as-is with 3d features imo for mobile and browser games, but anything additional always appreciated.
Excuse me.. Did you did 3D SAT collisions or AABB collisions?